Dr. Yimtubezinash W/AmanuelDr. Daniel AsratNegero Gemeda2021-09-082023-11-052021-09-082023-11-052012-06http://etd.aau.edu.et/handle/123456789/27835Background: Contamination of food commodities with spoilage fungi presents a problem of global concern, since the growth and metabolism of these organisms can cause serious food-borne intoxications and a rapid spoilage of food products. Aspergillus species, a kind of opportunistic fungi linked to food spoilage are the leading cause of infection, mycotoxicosis and economic loss. Mycotoxins they produce are responsible for cancers and many diseases affecting the gastrointestinal, urogenital, vascular, kidney, and nervous systems. Many efforts have been exerted in attempting to control Aspergillus infection by using synthetic chemicals, however, its application has led to a number of environmental and health problems because they are themselves carcinogenic, teratogenic, and highly toxic with long degradation periods. As a result there should be continuous search for safe preservatives from natural products. For this purpose essential oils could be a possible source of new novel antimicrobial as they are rich in chemical constituents that have antifungal activity and seldom accumulate in the environment. Objective: The aim of this study was to assess effect of essential oils on Aspergillus spore germination, growth and mycotoxin production of isolates from food commodities. Method: In vitro antifungal assay and antiaflatoxigenic assay of essential oils that are obtained by hydrodistillation was carried out using poisoned food techniques, spore germination assay, agar dilution assay, aflatoxin arresting assay and mycelial weight inhibition assay on Aspergillus flavus, Aspergillus fumigatus and Aspergillus niger. In vivo animal model was also conducted to see the safety limit of essential oil. Result: A. flavus, A. fumigatus and A. niger were isolated from a total of 36 food commodities. Cymbopogon martinii, Foeniculum vulgare, Lippia adoensis Hochst. var. koseret, Rosmarinus officinalis, Ruta chalepensis and Trachyspermum ammi essential oils were tested against seven isolates of aflatoxigenic Aspergillus species. T. ammi oil showed highest antifungal activity followed by Lippia adoensis Hochst. var. koseret. A hundred percent mycelial inhibition was recorded at 1µl/ml against A. niger and A. flavus; and 0.5µl/ml against A. fumigatus by T. ammi essential oils. Moreover, complete inhibition of spore germination of toxicogenic strains of A. flavus, A. fumigatus and A. niger was achieved with this essential oils at a concentration of 0.5µl/ml, 1 µl/ml and 1µl/ml, respectively. T. ammi oil also showed significant antiaflatoxigenic potency by totally inhibiting aflatoxin production from A. niger and A. flavus at 0.5 and 0.75µl/ml, respectively. C. martini, F. vulgare, L. adoensis Hochst. var. koseret and T. ammi essential oils as antifungal were found superior over chemical synthetic preservative. Moreover, a concentration of 5336.297µl/kg body weight was recorded for LC on mice indicating the low mammalian toxicity and strengthening traditional use of this plant as safe food preservative. Conclusion: The present study revealed that essential oils from T. ammi can be a potential source of safe natural food preservative for food commodities. For large scale utilization further studies are recommended to explore its activity on other toxigenic fungal species, mechanism of action and chronic toxicity of the oil.en-USAspergillus species, Essential oils, food spoilage, mycotoxin, preservativesThesis